This invention relates generally to shaft-mounted bearings, and more particularly to bearings having hexagonal and square inner race bores with elastomeric O-rings for mounting on hexagonal and square shafts.
Multi-sided bore bearings are commonly used in numerous applications. One such particular use is in agricultural machinery, such as for example, with disc harrows. The multi-sided bore within the inner race of such bearings is positioned over a mid-portion of a complementary multi-sided shaft to prevent the motion of the inner race relative to the shaft. In such bearings, it is desirable to have the inner race fit with the shaft on which it is mounted so that play between the inner race and the shaft is eliminated.
While the dimensional tolerance between the shaft and the interior surfaces of the inner bore will vary, the tolerance or play is approximately 0.005 inch. Variations in the bore dimensions may be due to distortions caused by broaching the bores in the soft state before hardening or to the heat treatment of the inner race after broaching. Also, broach tool tolerances, tool wear and gauging errors may add to tolerance build-up which results in the play between the shaft and the bore causing an undesirable amount of noise during operation.
Under ideal circumstances, the shaft and the inner bore would fit perfectly but as the dimensional tolerance gets tighter, the costs of achieving the tighter tolerance increases. Thus, the provision of a low cost bearing using current manufacturing techniques generally means there will be some play between the shaft and the central bore of the inner race. Present manufacturing methods provide that all bearings are made with a bore no larger than the maximum size of the shaft to be fitted. The shafting is generally cold drawn and has an associated dimensional tolerance of approximately 0.004 inches. Thus, if a particular shaft is 0.004 inch under nominal size and a bearing bore is 0.005 inch over nominal size, the result is in an undesirable amount of play.
The manufacturing clearance between the shaft and the central bore may adversely affect the bearing life, noise, shaft threading, and maximum rotational speed of the bearing. Additional clearance may result from the wear of the shaft or the bore of the bearing during use, increasing the adverse effects. A number of means for preventing motion of the inner race relative to the shaft such as an eccentric collar, cam lock, or screw set on the collar result in increased cost and require additional axle length. In addition, such alternative retention devices may loosen during use and allow the inner race to rotate with the shaft. It is thus desirable to provide a means for reducing the noise problem that exists with bearings having multi-sided inner race bores.
The foregoing illustrates limitations known to exist in the present bearings for mounting on multi-sided shafts. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereafter.